New Faint Optical Spectrophotometric Standards. Hot White Dwarfs from the Sloan Digital Sky Survey
New Faint Optical Spectrophotometric Standards. Hot White Dwarfs from the Sloan Digital Sky Survey
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新的微弱光学分光光度标准品。
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发表时间：
2009
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通讯作者：
J. A. Smith
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作者：
C. Prieto;I. Hubeny;J. A. Smith
利用模型大气可以精确地预测纯氢（DA）热白色矮星的光谱能量分布。这使得有可能通过宽带光度观测来缩放理论光谱形状来定义分光光度校准器-这是一种成功地用于哈勃太空望远镜（HST）机载光谱仪的策略，使用三种主要的DA标准。为了增加天空中校准器的密度而引入的非DA二级标准的绝对通量需要参考一级标准，但更好的解决方案是采用分散在天空中的DA恒星网络。我们在斯隆数字巡天（SDSS）的第六次数据发布中搜索蓝色天体，并拟合DA模型通量以确定合适的候选者。在分析许多这样的恒星时需要考虑红化。我们提出了一个清单的9个纯氢白色矮星的绝对通量与估计的不确定性低于3%，包括4个对象的估计误差<2%，作为候选人的光谱标准在14 < g < 18，并提供基于模型的通量缩放，以匹配SDSS宽带通量为每个。我们采用相同的方法，三个HST DA标准，连接零点的绝对通量UGR的幅度从测光与美国海军天文台1米望远镜转换。对于这些恒星，我们估计光学的不确定性<1%，与HST校准所采用的通量具有良好的一致性。
The spectral energy distributions for pure-hydrogen (DA) hot white dwarfs can be accurately predicted by model atmospheres. This makes it possible to define spectrophotometric calibrators by scaling the theoretical spectral shapes with broad-band photometric observations – a strategy successfully exploited for the spectrographs onboard the Hubble Space Telescope (HST) using three primary DA standards. Absolute fluxes for non-DA secondary standards, introduced to increase the density of calibrators in the sky, need to be referred to the primary standards, but a far better solution would be to employ a network of DA stars scattered throughout the sky. We search for blue objects in the sixth data release of the Sloan Digital Sky Survey (SDSS) and fit DA model fluxes to identify suitable candidates. Reddening needs to be considered in the analysis of many of these stars. We propose a list of nine pure-hydrogen white dwarfs with absolute fluxes with estimated uncertainties below 3 per cent, including four objects with estimated errors <2 per cent, as candidates for spectrophotometric standards in the range 14 < g < 18, and provide model-based fluxes scaled to match the SDSS broad-band fluxes for each. We apply the same method to the three HST DA standards, linking the zero point of their absolute fluxes to ugr magnitudes transformed from photometry obtained with the US Naval Observatory 1-m telescope. For these stars, we estimate uncertainties of <1 per cent in the optical, finding good consistency with the fluxes adopted for HST calibration.